System for optimized plant growth

ABSTRACT

A system for enabling controlled plant growth of plants in containers includes linear tracks spaced apart from each other by intervening supporting plates. Each track includes an array of blue and red LEDs affixed to a heat sink which can slide along the track to be positioned in a desired arrangement to the container beneath it. A controller for the LEDs is positioned between every other pair of tracks to control adjacent arrays of LEDs. The controller controls the LEDs to provide light of desired intensity and wavelength to the plants in the containers.

REFERENCE TO RELATED APPLICATION

This patent application claims priority from U.S. Provisional Patent Application Ser. No. 61/699,970, filed Sep. 12, 2012, and entitled “System for Optimized Plant Growth,” attorney docket 94551-851221 (000800US), the contents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

This application relates to technology for plant growth, and in particular, to a lighting system for optimized plant growth under controlled conditions.

Growing plants in a controlled environment is now a well-known technology. Greenhouses produce large quantities of flowers and vegetables which are distributed throughout the world. More recently, plants are being grown in yet further controlled environments, for example, where all of the light and nutrients are provided in a closed, essentially windowless structure. While such systems can use incandescent lighting, the reduced power consumption and higher efficiency of light-emitting diodes (LEDs) have made those the preferred choice for “indoor” greenhouses. We use the term “indoor” herein to refer to systems in which plants are grown with minimal or no exposure to ambient lighting—that is, systems in which essentially all of the light provided for plant growth is provided from artificial sources such as light-emitting diodes.

One example of this technology is known as “vertical” farming, i.e., growing herbs and vegetables in soil positioned in growing tubs placed in racks inside a closed building. This allows control of light, water, and nutrients. The closed environment dramatically reduces the amount of water required, while the ability to grow the produce on shelves of stacked racks dramatically reduces the square footage required to produce a given amount of produce. The light sources are positioned directly above and close (less than 12 inches) to the plants. This system is essentially a two-dimensional application of light; typically, the plants do not grow more than six inches in height before harvest. Accordingly, this application requires uniform light distribution from above radiating downward onto the target area. It also requires a reflective mounting structure to capture light reflected from the plants that would otherwise be lost, plus modularity for scaling, ease of installation, and low cost.

BRIEF SUMMARY OF THE INVENTION

Our system for enabling controlled growth of plants in containers includes a set of linear tracks spaced apart from each other. Supporting plates position the tracks in a parallel arrangement. Each track includes an array of blue and red LEDs affixed to a heat sink which can slide along the track to be positioned in a desired position to the container beneath it. A controller for the LEDs is situated between every other pair of tracks to control adjacent arrays of LEDs. The controller controls the LEDs to provide light of desired intensity and wavelength to the plants.

By making each track identical to all other tracks and making each supporting plate identical to all other supporting plates, the apparatus may be enlarged or reduced in a modular manner to an appropriate size for the configuration of the plant growth system. By positioning a light sensor in proximity to the containers and coupling it to at least some of the controllers, the intensity and wavelength of the light from the LEDs can be adjusted as needed for the particular plants and stage of plant growth. In addition, if the containers are labeled with identification tags, e.g., RFID, and also provide the apparatus with a tag sensor which detects the identification tags, the system can be controlled automatically. Furthermore, in some embodiments an environmental sensor is coupled to the controller to enable the controller to control an environmental variable such as temperature or humidity. Preferably, each array of light-emitting diodes includes only blue and red light-emitting diodes mounted on a heat sink, with a temperature sensor also mounted on the heat sink in communication with the controller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a light-emitting diode (LED) assembly for plant growth;

FIG. 2 is a perspective view of the assembly;

FIG. 3 is a diagram of an LED array strip;

FIG. 4 is a perspective view of the assembly as implemented in a typical environment; and

FIG. 5 is a block diagram illustrating a controller for the system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a top view of a light-emitting diode apparatus 10 used for plant growth. Shown in the diagram are a series of tracks 20 having spaced-apart side rails. Positioned within each track is a light-emitting diode (LED) assembly 30 which includes strips of LEDs affixed to a heat sink. The LED/heat sink assembly 30 is preferably not affixed to the track 20, enabling it to be positioned in the track in a desired relationship to the container beneath it. The LEDs are electrically coupled to controllers 40 disposed on the plates 50 of apparatus 10.

Each pair of tracks 20 is held in a fixed position with respect to other tracks by an intervening supporting plate 50. The plates 50 and tracks 20 enable a modular approach to the system in which additional sub-assemblies consisting of a plate and a track can be added to extend the length of the assembly as needed by the particular application.

FIG. 2 is a perspective view illustrating the apparatus in more detail. As shown, the individual tracks 20 each consist of a pair of L-shaped side rails 28 mounted in opposition to each other to provide a lower surface 29 upon which the LED assembly 30 is supported. The heat sink of each LED assembly 30 is not affixed to the track 20, but may be moved to and fro in the track 20 as indicated by the bi-directional arrow 32.

Also illustrated is a strip-shaped circuit board of LEDs 60 affixed to the lower surface of the heat sink. In the preferred embodiment, an LED circuit board of LEDs 60 consists of a linear row of blue LEDs disposed in parallel to a linear row of red LEDs. Wires, not shown, couple the strip of LEDs 60 to the controller 40. The intervening plates 50 between each pair of tracks 20 provide an attachment surface for the controller 40, and for tabs 22 on track 20.

FIG. 3 illustrates the LED circuit board 62 in more detail. Arranged in a linear manner along one edge of the circuit board 62 are LEDs 70 of a first color. Along the other edge of the circuit board 62 are LEDs 75 of a different color. Preferably the two colors are red and blue. Each circuit board of LEDs 70, 75 also preferably includes a thermistor 80, or other sensor, for measuring the temperature of the assembled circuit board 62 and heat sink. This allows more careful control of the temperature of the circuit board 62 and LEDs 60, enabling longer life for the LEDs. A connector 90 coupled to the LEDs 60 and the thermistor 80 enables electrical connections to be made between the LED assembly 60 and the controllers 40.

FIG. 4 is a diagram illustrating an application for the system described in FIGS. 1-3. As shown in the FIG. 4, a frame 100 supports a series of trays 110 in which plants are being grown. Each tray includes soil with appropriate nutrients and water added as necessary. Positioned linearly above the row of trays 110 is the apparatus 10 described in conjunction with FIGS. 1-3. Positioned above the apparatus 10 is another row of trays 109 supported on an additional portion 120 of the frame 100. Above the additional row of trays 109 is another LED assembly (not shown) to provide illumination to that row of trays.

A series of sensors 130 are mounted along the side rails of the frame 100 to detect the light emitted by the apparatus 10, and to detect environmental conditions in the vicinity of the apparatus. The sensors 130 are coupled to the controllers 40 to provide the controllers information about the color and intensity of the light being emitted by the strips of LEDs 60.

Generally, most plants absorb primarily blue and red light. With appropriate experimental testing and calculations, the apparatus described here provides an optimal mix of wavelengths of light ranging from all blue to all red, each with a controlled intensity. For example, some plants grow best with primarily blue light at the beginning of their growth, and later predominately red light. The apparatus described here enables such control.

The sensors positioned along the trays provide information about the color of the light being received. In addition, those sensors can also provide information about temperature, humidity, reflected light, carbon dioxide content, or other parameters of interest at the location of the trays with the plants. The sensors can provide feedback to control systems within the facility to raise or lower the temperature, humidity, carbon dioxide content, etc. In this manner, water use can be limited and power consumption made appropriate for the needs of the plant at the time.

Furthermore, in a preferred embodiment, an RFID tag can be added to each of the trays, where this identification is sensed by RFID sensors 160 on the frame 100. If the RFID tag information also provides information about the content of the tray, the light color and intensity of the LED emissions can be optimized for that particular plant type, even as the trays are moved to other locations on the supporting frames.

FIG. 5 is a block diagram illustrating a control system for the apparatus illustrated in FIGS. 1-3. As shown, the trays 110 containing plants are positioned under the strips of LEDs 60 which are supported by the frame 100. A light sensor (photo detector) 130 is positioned in proximity to the tray 110 to detect the light provided by the LEDs 60, and to relay that information over a connection 135 to a controller 40. Depending upon the particular plants and the stage of their growth, controller 40 provides signals over bus 140 to control the color and intensity of the light by controlling the LEDs 60. The particular tray 110 and its contents are identified to the controller 40 by an RFID tag 150. The RFID tag 150 communicates with an RFID sensor 160 which provides that information to a controller 40 using a connection 165. An environmental sensor 170 provides information to controller 40 about desired environmental variables, for example, temperature, humidity, carbon dioxide, etc. By coupling controller 40 to fans, heaters, or other apparatus, the environmental conditions in the vicinity of the trays 110 can therefore also be controlled.

Of course, while above we describe the structure and system described here in terms of an application for optimized plant growth, it will be apparent that the system described can have other uses, for example, in any circumstance in which controlling light output in a manufacturing process is important. For example, in the manufacture of products where photoresist is used, controlling the color and intensity of light can provide superior results. 

What is claimed is:
 1. Apparatus for providing controlled wavelength and intensity of light for use in a process involving exposure of items to light, the apparatus comprising: a first plurality of linear tracks spaced apart, disposed in a parallel arrangement, and separated from each other by plates; a first plurality of arrays of light-emitting diodes (LEDs), each array being positioned in one of the tracks; and at least one controller coupled to each of the first plurality of arrays of LEDs; wherein the controller controls the LEDs to provide controlled wavelength and intensity of light to the items.
 2. Apparatus as in claim 1 wherein each of the tracks is of a same size and shape, and each of the plates is of a same size and shape to enable enlarging the apparatus by adding additional tracks and additional plates to provide a desired size.
 3. Apparatus as in claim 1 wherein the at least one controller comprises a second plurality of controllers, the second plurality being one half the first plurality.
 4. Apparatus as in claim 3 wherein a controller is disposed on every other plate and coupled to an array of LEDs in tracks on each side of the controller.
 5. Apparatus as in claim 1 further comprising a light sensor positioned in proximity to the items and coupled to at least some of the controllers for controlling intensity and wavelength of the light from the LEDs.
 6. Apparatus as in claim 5 wherein the items are labeled with identification tags and the apparatus further comprises a tag sensor to detect the identification tags and communicate that information to at least one of the controllers.
 7. Apparatus as in claim 1 further comprising an environmental sensor coupled to the controller to enable the controller to control an environmental variable.
 8. Apparatus as in claim 1 wherein each array of LEDs includes LEDs which emit red light and LEDs which emit blue light.
 9. Apparatus as in claim 8 wherein each array of LEDs is mounted on a heat sink, and a temperature sensor is also mounted on the heat sink in communication with the at least one controller.
 10. Apparatus as in claim 2 wherein: each of the tracks comprises pair of L-shaped members having a first length facing in opposition to each other; the LEDs are affixed to a heat sink having a second length less than the first length; and the heat sink is positioned in the track and is movable along the track. 